Wouldn't it be nice if you could predict which chord would probably come next in a song?

I've got some good news for you.

It is possible. Not 100%, but somewhere on the order of 75% to 85% accurate.

That's because music has FORM -- like the skeleton that holds your flesh, muscles, and skin up. If you had no bones -- no skeleton -- your flesh and all the other parts of you would fall in a heap on the floor. Not a pretty picture. But because you DO have a skeleton, you are able to walk around and pretty accurately predict which way your next step will take you. It's the same in music. Music has FORM -- a skeleton to hold it up, hold it together. And that skeleton is made out of chords -- harmony -- the tonal center of the song or piece.

In any given key you can play in, there are PRIMARY CHORDS -- chords that occur way more than other chords. They are like family members of that particular key.

At your house, let's say you have 3 people in your family -- your spouse, your child, and you. On the same block, but down the street a few houses, lives your cousin and her family. At any given moment, who are the most likely people to be in your house?

Steve Martin? John McCain? Barry Bonds?

I don't think so.

It's possible, of course, but not too likely. If I had to guess, I would say it would be either you, your spouse, or your child. It might be your cousin down the street -- there's a much better chance of that than, say, Mel Gibson -- but my best odds would be to guess that the family members would be there.

It's the same way with chords. In any given key, there are 3 "family members" that are residents of that key -- the I chord, the IV chord, and the V chord. They are far and away the most likely chords to occur in any given key.

For example, if I am playing in the Key of C, and the first chord is the C chord and I have to guess what the next chord is, I would guess that it would be either the F chord or the G chord. Why? Because those are the other "family members". So we have narrowed the odds a great deal just by knowing who the members of the family are.

So how could I tell whether it should be F or G?

If the melody is a "B", then the chord is probably a G chord. Why? Because "B" is in the G chord, but is not in the F chord. If the melody is a "A", than I would guess that the chord is F. Why? Because "A" is in the F chord, but is not in the G chord. Does that mean that there are always just 3 chords in a song?

No, but there are literally hundreds of songs that are made of just 3 chords.

What if there are more than 3 chords in a song? What then?

We'll take that up in part 2 of this series of articles.

Duane Shinn is the author of over 500 music books and music educational materials such as DVD's, CD's, musical games for kids, chord charts, musical software, and piano lesson instructional courses for adults. His book-CD-DVD course titled "How To Play Chord Piano In Ten Days!" has sold over 100,000 copies around the world. He holds advanced degrees from Southern Oregon University and was the founder of Piano University in Southern Oregon. He is the author of the popular free 101-week online e-mail newsletter titled "Amazing Secrets Of Exciting Piano Chords & Sizzling Chord Progressions" with over 70,000 current subscribers.